Cataract surgery of the human eye lens is the most commonly performed operation world-wide, with about 20 million procedures performed a year. Cataract numbers increase more and more with aging society. Because of age as well as other factors such as UV radiation, the human lens becomes increasingly opaque until the patient becomes blind. Well-established cataract surgery, which is mostly done by phacoemulsification of the natural lens within the capsular bag and implantation of a new artificial intraocular lens, can avoid blindness and give patients clear vision again.
Before the onset of cataract, on-going growth and hardening of the natural human lens over time can reduce the ability of the lens to accommodate or change shape in order to see both distant and near objects. By the age of 40, the accommodation range can become less than 3 D, which strongly influences near vision in emmetropic eyes. This is called presbyopia. Reading glasses are helpful to overcome the effects of presbyopia, but don't address the root cause. Other approaches like multifocal intraocular lenses, multifocal corneal laser ablation profiles in LASIK (laser in situ keratomileusis) procedures, intracorneal inlays, Femtosecond (or other) laser incisions inside the corneal stroma like INTRACOR® or photothermal keratoplasty can regain near vision. These surgical treatment options are based on using multifocality to extend the depth of focus, but at a cost of contrast sensitivity or also requiring a monovision or micro-monovision.
Accommodating artificial intraocular lenses like AT-45 CrystaLens, Human Optics 1CU and others have been developed as a potential solution to recreate the accommodative response artificially, however, studies have shown that there is negligible forward movement of the lens and so any increase in near vision with these lenses comes from a small depth of field increase due to the asphericity in the lenses. Certainly, accommodative lenses have been unable to give the patient the 3 D of accommodative range that is required.
Lens capsule refill technologies are under development to bring a gel into the capsular bag after phacoemulsification of the natural lens. However, these lens capsule refill technologies cannot currently adjust the refractive power or the dimensions of this gel IOL accurately enough during the refilling process. There are also serious problems with posterior lens capsule opacification.
Over the last 10 years, femtosecond (or other) laser surgery of the human cornea has been introduced into clinical practice. Femtosecond (or other) laser technology uses the phenomenon of photodisruption to create microbubbles within the cornea to separate tissue. By scanning the laser spot, 3-dimensional cuts can be performed to create a flap as part of a LASIK procedure (U.S. Pat. No. 5,984,916) or also to cut out a precise intra-stromal lenticule, which can then be extracted through a small incision to correct the manifest refraction with the VisuMax femtosecond (or other) laser system (US 2008/0275433).
Femtosecond (or other) laser cataract surgery has also been successfully introduced in recent years. In this procedure, a femtosecond (or other) laser is used to open the anterior capsular bag by creating a centered, round, custom-designed anterior capsulotomy. Using a femtosecond (or other) laser has advantages over manual capsulotomy as the cut is more accurate. The femtosecond (or other) laser is then used to break up the cataract lens by making a crossed cut or by chopping the lens into tiny parts which can then be easily removed from the capsular bag (U.S. Pat. No. 7,351,241).
Femtosecond (or other) laser surgery for the treatment of presbyopia has also been proposed in the past. The main approach was to soften the natural human lens with theory that the lens would regain elasticity and accommodative amplitude. The lens softening can be done by cutting gliding planes or producing microbubbles in order to produce a more elastic sponge-like structure. (See: EP 1212022 B 1). This approach is mainly based on the Helmholtz model of accommodation where the stiffness of the lens material plays the most important role.